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From: Oleg Nesterov <oleg@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: mingo@kernel.org, tglx@linutronix.de,
	linux-kernel@vger.kernel.org, will.deacon@arm.com,
	mpe@ellerman.id.au, bigeasy@linutronix.de, gkohli@codeaurora.org,
	neeraju@codeaurora.org
Subject: Re: [PATCH 2/2] sched: Introduce set_special_state()
Date: Tue, 1 May 2018 15:59:24 +0200	[thread overview]
Message-ID: <20180501135924.GA12696@redhat.com> (raw)
In-Reply-To: <20180501095054.GD12235@hirez.programming.kicks-ass.net>

On 05/01, Peter Zijlstra wrote:
>
> The only code I found that seems to care is ptrace_attach(), where we
> wait for JOBCTL_TRAPPING to get cleared. That same function has a
> comment about hiding the STOPPED -> RUNNING -> TRACED transition. So I'm
> assuming it needs to observe TRACED if it observes !TRAPPING.

Yes, exactly.

> But I don't think there's enough barriers on that end to guarantee this.
> Any ->state load after wait_on_bit() is, afact, free to have happened
> before the ->jobctl load.

do_wait() does set_current_state() before it checks ->state or anything else.

Oleg.

  reply	other threads:[~2018-05-01 13:59 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-30 14:17 [PATCH 0/2] sched,kthread: Fix TASK_PARKED and special sleep states Peter Zijlstra
2018-04-30 14:17 ` [PATCH 1/2] kthread: Fix kthread_parkme() wait-loop Peter Zijlstra
2018-04-30 14:17 ` [PATCH 2/2] sched: Introduce set_special_state() Peter Zijlstra
2018-04-30 16:45   ` Oleg Nesterov
2018-04-30 19:40     ` Peter Zijlstra
2018-05-01  9:50       ` Peter Zijlstra
2018-05-01 13:59         ` Oleg Nesterov [this message]
2018-05-01 14:22           ` Peter Zijlstra
2018-05-01 15:10             ` Oleg Nesterov

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